Conventional resin molding semiconductor devices have been manufactured by mounting semiconductor elements on a substrate, connecting electrodes on each semiconductor element to electrodes on the substrate via bonding wires, and molding the integrated semiconductor device with resin so as to wrap it. Specifically, the conventional resin molding semiconductor device has been manufactured by executing a resin molding process (transfer mold) comprising installing the semiconductor device in a cavity of a mold, injecting and filling a molten resin into the cavity through a gate, and hardening the resin.
As the advanced information-oriented society develops, stronger demands have been made to reduce the sizes and thicknesses of and to improve the functions of a group of products in the small electronic equipment field which are used in the advanced information-oriented society. In connection with the manufacture of semiconductor elements, key devices for the group of products, a reduction in the sizes and pitches of semiconductor elements has been strongly demanded. Resin molding semiconductor devices with the semiconductor elements mounted thereon are strongly demanded to have a structure including long wires or narrow pat pitch connections and in which electrodes on the semiconductor elements are electrically connected to many electrodes mounted on the substrate.
Requests have also been made for structures such as POP (Package On Package) in which a plurality of semiconductor devices are stacked and electrically connected together in order to provide improved functions.
A common method for manufacturing the resin molding semiconductor device has been to inject resin into the cavity of the mold through the side surface of the cavity. However, with this method, during resin injection, the resin flows along the direction in which wires are arranged. Consequently, a wire coming into contact with the resin may be swept away by the resin to flow toward the adjacent wire. In this case, the wires contact each other to cause a short circuit.
A manufacturing method for inhibiting such a problem is proposed by, for example, Japanese Patent Laid-Open No. 2005-347514. According to this method, a gate is formed on a surface of the cavity which is located opposite a front surface of the semiconductor element and the resin is ejected from the gate toward the front surface of the semiconductor element.
With reference to FIGS. 14A to 14C and 15, description will be given of a method for manufacturing such a conventional resin molding semiconductor device as described above. FIG. 14A is a plan view of a resin molding semiconductor device having a gate, that is, a resin injection port, formed on a surface of a cavity which is located opposite a front surface of each semiconductor element. FIG. 14B is a sectional view of the resin molding semiconductor device taken along line A-A′ in FIG. 14A. FIG. 14C is an enlarged plan view of a portion B in FIG. 14A. FIG. 15 is a sectional view showing a production equipment of the resin molding semiconductor device.
As shown in FIGS. 14A to 14C and 15, the resin molding semiconductor device is manufactured by mounting a semiconductor element 52 on a substrate 51 and injecting a molding resin 54 toward a front surface of the semiconductor element 52 through a gate (resin injection port) 53 formed on a surface of a cavity 64 in molds 61, 62, and 63 which is located opposite the semiconductor element 52, to fill the cavity 64 with the molding resin 54. Here, reference numeral 55 in FIG. 14B denotes a wire, and reference numeral 56 denotes a solder ball. In FIG. 15, reference numerals 61, 62, and 63 denote an upper mold, an intermediate mold, and a lower mold. Reference numeral 65 denotes a plunger that pushes the molding resin 54 into the cavity 64 through a runner 66. Reference numeral 67 denotes an air vent portion (air release passage) formed in an area of the upper mold 61 which is located opposite a front surface portion (top surface portion) of the substrate 51.
In connection with such a resin molding semiconductor device, for example, Japanese Patent Laid-Open No. 2000-124239 proposes the production of a resin molding semiconductor device involving executing one molding process to mold a plurality of semiconductor elements 52 in order to reduce production time and subsequently cutting the semiconductor elements 52 off from one another to obtain the finished products.
To implement POP (Package On Package) on the conventional resin molding semiconductor device, external terminals need to be provided on a front surface of the substrate 51. However, with the conventional method for manufacturing a semiconductor device, air resulting from injection of the molding resin 54 is discharged from the air vent portion 67, formed on the side surface of the cavity 64. Thus, unfortunately, resin burrs 57 (see FIG. 14C) may be discharged together with air and adhere to the external terminals on the substrate 51. This may prevent electric connections.
Further, when an attempt is made to locate the external terminals in an area where no resin burrs 57 will be formed, the arrangement of the external terminals is limited. This may disadvantageously complicate wiring to increase manufacturing costs or increase the area of the substrate, preventing the resin molding semiconductor device from being miniaturized.
Another problem is that the resin burrs 57 may adhere to the external electrodes to reduce yield, preventing improvement of productivity.